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aarjan
10-16-2003, 03:16 AM
Last night had a discussion with my girlfriend (yeah strange things happen when you put two aikidoka in one bed ;)). We know that hitting the mat with your hand when you make a breakfall results in a softer and easier landing, but why? What happens to your body when you do that? Anyone???

Thanx in advance,

Thalib
10-16-2003, 04:11 AM
I don't hit the mat any longer. It just hurts my hand and arm.

Now, I place my hand on the ground.

If I place my hand on the ground after my body hits it, it is useless.

If I place my hand on the ground before my body hits it, I could use it as a measurement as how far off I am from the ground and/or I could use it to absorb part of the energy before my body hits the ground.

I have other uses for my hand other than to touch the ground, like to keep hold on a person or a weapon. The circular motion, when done properly, is actually enough to absorb the harmful energy. I only touch the ground with my hand when it is necessary, not all the time.

sanosuke
10-16-2003, 04:19 AM
have experienced splatting concrete floor when doing breakfall. I tell you man, it daaamn hurts, now eventhough i'm still hitting the mat during breakfall, i tried my best to use my knife-hand instead of my palm.

Yann Golanski
10-16-2003, 04:52 AM
<pedentic:mathematician>

As far as I know, it has to do with mechanics, specifically conservation of momentum. As tori thrown uke, uke gains momentum towards the floor. To this gravity adds it pull as per usual.

When you collide with the floor the momentum you have is conserved. Most of that momentum is transfered to the mats but some goes into your body. The arms hitting the mat, or more acuratly bouncing off the mat, is a way to take momentum out of your torso and onto your arms.

Conversly, when you are relaxed momentum is transfered throughout your body and your body bounced gently off the mat. If you tense, then the momentum hits the first tense group it finds and stops there. Hence damage occurs to that area.

It is possible to just bounce off the amt when someone is throwing you. All you need is an intuitive knoweldge of how momentum works.

</pedentic:mathematician>

Of course, hitting the ground only works when you have soft matts. On a hard structure (asphalt, concreeet, wood, etc...) it will result in pain and no gain. If you can manage without hitting the ground, then do so as it will be usefull if you have to ukemi in the real world(tm). But I would consider this advenced ukemi.

BTW, if your hand are the first point of contact as you fall then your wirst is going to snap. Be carefull.

Nick Simpson
10-16-2003, 05:54 AM
I was being thrown out of Jujinage the other day and couldnt hit the mat with my hands at several times, but I didnt seem to get battered too badly, seemed to me as long as I breathed out then I was ok.

The times I've been thrown on concrete Ive slapped the ground pretty hard without breaking anything, just a little stinging for my efforts, Id rather have that pain in my hand than in my back though.

As far as I can tell, it seems easier to get away without slapping the ground when your on mats (obviously cos there softer) but on harder surfaces it seems to be neccesary to slap, in my limited opinion.

ian
10-16-2003, 08:59 AM
Yep - I've same experience as Nick. I've fallen heavily on concrete and it makes your forearm sting like anything when you hit it - but everything is fully functional and you are able to stand up and fight.

I think hitting the mat should be a last resort (I find I get punch drunk on long courses if I hit the mat all the time when I could actually roll). However if you are shown very fast and land in a flat fashion, there is no way to roll - hitting the ground with the fore-arm is better than breaking your hip, winding yourself or damaging your spine.

I know many people hit the mat with their hand only. Due to the low surface area this can be more painful than using your whole forearm and hand (esp. if you have nice muscley fore-arms from bokken work which cushions the blow).

Basically from a physical point of view - your body is going to hit the ground with a certain force. If you have small objects (hip bones, vertebrae, coccyx) hitting the ground, all the force is concentrated in one area. Although slapping the mat concentrates the force into your fore-arm, it is fleshy and can resist the impact better than bone. Ideally we would distribute the force evenly across our body (i.e. rolling!)

Ian

Kevin Wilbanks
10-16-2003, 09:28 AM
I've trained on hard dirt and concrete a few times. Slapping the ground hurt my hand and forearm enough that I stopped doing it almost right away. I'm not sure if this contradicts what Nick and Ian are saying or not. Perhaps they are talking about taking particular types of falls where one has to slap to avoid body damage.

If one is not surprised or dealing with an awkward trapped-limb situation, I think it is possible most of the time to use soft/wide leg ukemi principles to make for a less ballistic fall and avoid slapping - the arm is used more to reach out and push/deccelerate. It is certainly something that has to be learned over time though. I did strict traditional ukemi for most of my Aikido time. During the transition, I've trained on hard mats, and found that using a tense slap-ready body made for more comfortable falls. In-between attempts at relaxed falls were murder on a hard surface.

Greg Jennings
10-16-2003, 10:54 AM
Another mathematician/engineer being overly technical:

---

I get the hand down to "trade down for around".

That is, I try to dissipate the energy by transforming the vertical component into a rotational component.

Sometimes the hand goes down gently, like I'm "feeling" for the ground.

Sometimes I really have to hurry to get it down and it turns into a slap. The slap is not what I'm after, it's just a by-product of being in a hurry.

Regards,

Nick Simpson
10-16-2003, 04:28 PM
When ive been thrown on concrete it was into a forward rolling breakfall with no supporting hand touching the ground first (Hyaku Ukemi), works just fine, maybe My body will tell me different when im 40 :p

Nick Simpson
10-16-2003, 04:32 PM
Oops, sorry, that was in relation to what Kevin asked about what kind of breakfall.

akiy
10-16-2003, 05:51 PM
When ive been thrown on concrete it was into a forward rolling breakfall with no supporting hand touching the ground first (Hyaku Ukemi)
Can you please tell me what "hyaku" means in this context? Do you have the kanji characters for the term? I can't come up with anything (outside of "100") that might fit...

-- Jun

Nick Simpson
10-17-2003, 04:29 AM
Ah, I spelt it wrong, my apologies, what I meant was: Hayaku Ukemi, which as far as Im aware is the Yoshinkan term for fast breakfall/vertical flip. Sorry about that, maybe some of the yoshinkan guys could help?

aarjan
10-17-2003, 06:00 AM
Thanx to all that responded. I understand the loss of energy but what happens to your body? Easier to relax, tension on the right moment?? I do it without thinking but my girlfriend just mimics the movement but she doesn't feel and understand the benefit.

By the way, the type of ukemi I was refering to is ukemi from koshi nage and for example ashi harai in judo. Can't imagine doing that one on concrete... Ouch

justinm
10-17-2003, 08:10 AM
Ah, I spelt it wrong, my apologies, what I meant was: Hayaku Ukemi, which as far as Im aware is the Yoshinkan term for fast breakfall/vertical flip. Sorry about that, maybe some of the yoshinkan guys could help?
I'd usually spell it Hiyaku, meaning "jumping", however my spolling is not a strengf in any langwage

jducusin
10-17-2003, 10:24 PM
I believe that on it's own, hyaku/hayaku means "hurry" or "quickly"...but then, I've learned all my Japanese from anime, so... ;)

Abasan
10-22-2003, 12:01 AM
I think hitting with the knife hand is a recipe for disaster and broken fingers/wrist.

Still trying hard to find that elusive, use hand to decelerate breakfall. I don't even have time to think when being thrown into a breakfall, its totally instinctive reaction to slap my hand and yes it hurts plenty on concrete. Sometimes part of my fingers bleed internally after slapping concrete.

ikkainogakusei
10-27-2003, 10:29 AM
<obsessed:kinesiologist>

Okay, I'm better at axplaining the neuromotor end than the biomechanical end of this so if there is a mistake, let me know, but as far as I understand it it goes like this. When we fall, if we can't redirect our fall into a roll, we might choose a high fall. In this case we must change the momentum. An important part of this is impulse. The impulse equals the change in momentum produced by the force in a certain time interval.

Change in momentum = (mass) x (change in velocity) = (force) x (change in time)

The slap (in a high fall or even hard roll) can help with the dispersion of Kinetic energy by having a short impulse 'slap'. I believe that the makeup of the lighter, flat, but cushioned and bony (in just the right places) hand is better fit to disperse this kinetic energy

Kinetic Energy = (1/2) x (mass) x (velocity)^2 KE = (1/2) mv^2

So we slap to redistribute force away from our trunk, which is not so well built for collision. Also, the impulse explains why it is incredibly painful to do the same slap on concrete or tile or whathaveyou. When you slap a cushioned surface like a mat, that mat bends and lengthens the deceleration time in which the contact is made with your hand, concrete does not, therefore the impulse is even greater and the Ground Reaction Force is much greater on an unforgiving surface.

Also, hand first is okay if you -=really=- know what you are doing and your timing is -=really=- good. It won't do the same type of dispersion and there is a great potential for a joint lockup and long axis force transfer along the arm. (=bad news)

Blade hand slap reduces the distribution to a smaller surface area (same force but more per square inch of contact) and makes it easier to not be in the appropriate shoulder rotation position. Palm-down slaps also put the gleno-humeral part of the shoulder in a good position to deal with the impact. (I know supination/pronation can be independant, but it happens that people do rotate more overall.)Having the arm in a 45 degree angle to the trunk also helps.

Overall however, you need to figure what is least damaging/painful to you.

Oh, you asked what happens to your body when you slap? It misses out on some of the Ground Reaction Force being transferred to your spine, some still gets there, but slap, Kiai, and good form keeps things from snapping, popping, breaking, or ripping.

:ai:

Lan Powers
10-27-2003, 06:24 PM
I don't mean to sound too much a novice, but,

What is up with training/ukemi on concrete? Several have mentioned it, and I can't imagine "voluntarily" taking a hi-fall there. If sensei says roll out of this on pavement.... then ok (shudder) but it seems unlikely to me.

Am I missing something? Are you folks training on those surfaces for a reason?

Did it help your ukemi?

Asking politely.......

Lan

Jeanne Shepard
10-27-2003, 07:08 PM
Yeah, are you guys just crazy, or is there a good reason to do ukemi on concrete?

Jeanne

Jeanne Shepard
10-27-2003, 07:09 PM
By the way, I hear in their uchi deschi days, the now shihan uused to throw themselves out of the windows to practice high falls. The story says they were drunk too.

Jeanne

Thalib
10-27-2003, 07:41 PM
We usually do a demonstration each year on the university parking lot. We did use mattresses, that is until we stepped on it. The sun had been baking the mattresses for a few minutes.

Those mattresses are hot enough to fry eggs, teppanyaki style. First time we did it in 1999, a female student burned her foot on the mattress. We removed the mattresses and did the rest of the demo on concrete.

We still try to use mattresses the next year. It was still hot enough to fry an egg on. After that, we don't even bother using any mattreses.

Last time, we had to use mattresses for the outdoors enbukai during Matsuri. Because this is not our own enbu, there are other martial art styles participating, we are obligated to use the mattresses. Knowing from our experience we got jika-tabi for our demo.

Abasan
10-27-2003, 10:37 PM
Its not the geek factor talking. Ukemi on concrete is not an issue, breakfalls are. But we don't do it voluntarily.

You know when you do seminars, sometimes a hall is used with concrete floors and your mats are the interlocking ones? Ok, so the mat is crowded, your partner throws you right at the age, and you land halfway outside the mat. That's when you are most likely to experience breakfall on concrete.

Nick Simpson
10-28-2003, 05:36 AM
It was a bet. Im known for taking quite high ukemi on the mat so someone said " I bet you wouldnt do one of those if I threw you on this concrete. " He was offering a couple of drinks and it seemed like a good idea at the time so I did it. After that it didnt bother me so I still do it when the opportunity presents itself. For practicality, Id say it helps confidence, if you can do it on concrete what have you got to be scared of on the mat? (though I am also a little crazy Jeanne ;) )